Rapid isothermal annealing of As-, P-, and B-implanted silicon Page: 4,164
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doses of 1.0 x 10'5/cm2 and annealed with a heater set point
temperature of 1150 "C. The SiO2 cap was removed in hydro-
fluoric acid prior to the sheet resistance readings. The mini-
mum sheet resistance is achieved between 12.5 and 15 sec.
The sheet resistance remains constant on the half of the wa-
fer that was capped with SiO2. Figure 3(b) shows the As
profiles, obtained by RBS, on the capped and uncapped por-
5 10 15 20 25 30
FIG. 2. Sheet resistance vs anneal time for 75As (100 keV) implanted Si after
annealing with a heater set point temperature of 1150 "C.
across the 3-in. wafers was better than 2%. The minimum
sheet resistance value of 85 2 /sq obtained on wafers im-
planted to a dose of 1.0X 10'5/cm2 can be compared to a 90
12 /sq sheet resistance achieved by conventional furnace an-
nealing at 1000 C for 10 min in N2. A sheet resistance read-
ing was obtained after 5 sec for the highest dose and not on
lower doses, because this wafer reached a high temperature
(> 900 "C) sooner. (See Fig. 1.)
Rutherford backscattering and ion channeling analysis
have been used to show that complete annealing of the amor-
phous layer created by a 1.0 X 10'5/cm2 As implant occurs
only after a 15-sec exposure.12 This explains the high sheet
resistance readings for shorter exposure times since the do-
pant resides in an amorphous or heavily damaged layer. This
further confirms that the wafer temperature does not exceed
900 C for exposure times less than 10 sec. Channeling analy-
sis on samples subjected to a 15 sec or longer exposure time
showed no evidence of residual damage or defects.12 The
scattering yield ymin < 5%) was only slightly higher than
the yield obtained on virgin unimplanted silicon
(%min = 3%).
In Ref. 12 we stated that for a 1.0 x10'5/cm2 As im-
plant, no loss of As occurred for exposure times of 5 or 10 sec
and essentially no diffusion was observed. However, for a 15-
sec exposure some diffusion occurs and - 8% of the total As
was lost as determined by RBS. Longer exposure times pro-
duced greater diffusion and more dopant loss. This loss of
dopant explains the rise in Rs for exposure times greater
than 15 sec.
To prevent the loss of As from implanted wafers a series
of experiments was performed where one half of each wafer
was capped with 0.05 pm of deposited oxide subsequent to
the implant and prior to the anneal. Figure 3(a) presents
sheet resistance versus exposure time for wafers implanted to
S 10 19
5 10 15 20
75As (100 KeV, 1 n 10 15/cm2)
RIA 1150C 30 SEC.
--- WITH SiO2 CAP
WITHOUT SiO02 CAP
0.0 0.10 0.20
FIG. 3.(a) Sheet resistance vs exposure time for "As (100 keV, 1.0X 10'5/
cm2) implanted Si. Half of each wafer was capped with SiO2 prior to the
anneal. The graphite heater set point was 1150 "C. (b) 75As profiles mea-
sured by RBS after a 1150 eC set point, 30-sec exposure. The dashed curve
was the profile obtained on the half of the wafer that was capped. The solid
curve was obtained on the uncapped portion of the wafer. Approximately
30% of the As was lost from the uncapped portion.
4164 J. Apple. Phys., Vol. 55, No. 12, 15 June 1984
Wilson et al. 4164
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Wilson, Scott R.; Paulson, W. M.; Gregory, R. B.; Hamdi, A. H. & McDaniel, Floyd Del. (Floyd Delbert), 1942-. Rapid isothermal annealing of As-, P-, and B-implanted silicon, article, June 15, 1984; [College Park, Maryland]. (digital.library.unt.edu/ark:/67531/metadc139472/m1/3/: accessed April 24, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT College of Arts and Sciences.